The intent of this Chapter is to answer simple questions related to the definition of sound, its sources, quantification and methods of measurement, acceptable levels of sound, differences between sound and noise, etc. Of course, when verbalizing such questions, the solutions for sound control will be naturally unfolded to readers. This Chapter is intended to thoroughly separate myth from reality. The Chapter also introduces the International Building Code (IBC) requirements for sound insulation in buildings. State of the art construction details for CLT walls and floor/ceiling assemblies generally meeting IBC requirements are provided herein and are based on results of tests performed in various laboratories in the world and in the field by FPInnovations. A step by step construction practices guide then leads the reader towards the final goal, which is the occupants' satisfaction. We expect that after reading this Chapter, the reader will be in a position to acknowledge that CLT buildings can achieve satisfactory sound insulation levels if proper design and installation are followed. Note that, considering the short history of CLT construction, the journey is only beginning.
The environmental footprint of CLT is frequently discussed as potentially beneficial when compared to functionally equivalent non-wood alternatives, particularly concrete systems. In this Chapter, the role of CLT in sustainable design is addressed. The embodied environmental impacts of CLT in a mid-rise building are discussed, with preliminary results from a comprehensive life cycle assessment (LCA) study. We also discuss other aspects of CLT's environmental profile, including impact on the forest resource and impact on indoor air quality from CLT emissions. The ability of the North American forest to sustainably support a CLT industry is an important consideration and is assessed from several angles, including a companion discussion regarding efficient use of material. Market projections and forest growth-removal are applied to reach a clear conclusion that CLT will not create a challenge to the sustainable forest practices currently in place in North America and safeguarded through legislation and/or third party certification programs. To assess potential impact on indoor air quality, CLT products with different thicknesses and glue lines were tested for their volative organic compounds (VOCs) including formaldehyde and acetaldehyde emissions. CLT was found to be in compliance with European labeling programs as well as the most stringent CARB limits for formaldehyde emissions. Testing was done on Canadian species, as there was no U.S. supplier of CLT at the time of this writing; because VOC emissions are affected by species, this work should be repeated from products made from different species.
Cross-laminated timber (CLT) is proving to be a promising solution for wood to compete in building sectors where steel and concrete have traditionally predominated. Studies at FPInnovations found that bare CLT floor systems differ from traditional lightweight wood joisted floors with typical mass around 4 lb./ft2 (20 kg/m2) and fundamental natural frequency above 15 Hz, and heavy concrete slab floors with a mass above 40 lb./ft2 (200 kg/m2) and fundamental natural frequency below 8 Hz. Based on FPInnovations' test results, bare CLT floors were found to have mass varying from approximately 6 lb./ft2 (30 kg/m2) to 30 lb./ft2 (150 kg/m2), and a fundamental natural frequency above 9 Hz. Due to these special properties, the existing standard vibration controlled design methods for lightweight and heavy floors may not be applicable for CLT floors. ...
Cross-laminated timber (CLT), a new generation of engineered wood product developed initially in Europe, has been gaining increased popularity in residential and non-residential applications in several countries. Many impressive low- and mid-rise buildings built around the world using CLT showcase the many advantages this product has to offer to the construction sector. In this Chapter, we put forward an introduction to CLT as a product and CLT construction in general, along with different examples of buildings and other structures made with CLT panels. CLT is now available in North America and several projects already built in Canada and the United States, using CLT, are presented in this Chapter. An assessment of market opportunity for CLT based on the latest construction statistics for the United States is also presented.
This Chapter provides general information about the manufacturing of CLT that may be of interest to the design community. The information contained in this Chapter may also provide guidance to CLT manufacturers in the development of their plant operating specification document. Typical steps of the CLT manufacturing process are described, and key process variables affecting adhesive bond quality of CLT products are discussed. The manufacturing, qualification, and quality assurance requirements in accordance with the American National Standard for Performance-Rated Cross-Laminated Timber, ANSI/APA PRG 320, are discussed.
This Chapter focuses on a few fastening systems that reflect present-day practices, some being conventional, while others are proprietary. Given the recent introduction of CLT into the construction market, it is expected that new connection types will be developed over time. Issues associated with connection design specific to CLT assemblies are presented. The European design approach is also presented and the applicability of the National Design Specification (NDS) for Wood Construction design provisions for traditional fasteners in CLT such as bolts, dowels, nails, and wood screws are reviewed and design guidelines are provided. Several design examples are also given at the end to demonstrate how connections in CLT can be established using current NDS design provisions.
Building using cross-laminated timber (CLT) began in Europe about two decades ago and has used a variety of methods for structural analysis. Experimental testing methods were the most accurate, yet they lacked versatility because changes in lay-up, material, or even manufacturing methods could cause a need for new testing. Consequently, three analytical approaches have been created and are commonly used in Europe as none have been universally accepted to date. ... In the United States and Canada, the product standard (Standard for Performance-Rated Cross-Laminated Timber - ANSI/APA PRG 320) has adopted the Shear Analogy method to derive composite bending and shear stiffness properties.
Cross-laminated timber (CLT) is an innovative wood product that was developed approximately two decades ago in Europe and has since been gaining in popularity. Based on the experience of European researchers and designers, it is believed that CLT can provide the U.S. market the opportunity to build mid- and high-rise wood buildings. This Chapter presents a summary of past research and state-of-the-art understanding of the seismic behavior of CLT. As a new structural system to the United States, the design of CLT for seismic applications is expected to be made through alternative method provisions of the building codes. Efforts to develop seismic design coefficients for use in the equivalent lateral force procedures in the United States are underway. Nonlinear numerical modeling of CLT is presented and used to provide and indication of the effect of designing with different R-factors. Using nominal CLT wall capacity values derived from isolated wall tests, the illustrative example showed that an R-factor of approximately 2 can result in a low probability of collapse (less than 10 percent) at MCE intensity.
Cross-laminated timber (CLT) construction is a relatively new process. There is therefore very little specific technical documentation for the erection of structures designed and built with CLT panels. Current CLT manufacturers provide recommendations on lifting systems for the installation of prefabricated wood assemblies. However, technical documents currently available mostly come from Europe or Canada and may appear incomplete to some design professionals and builders/contractors in the United States. This Chapter presents a variety of lifting systems that can be used in the construction of structures using CLT panels. We discuss the basic theory required or suggested for proper lifting techniques. In addition, we introduce various tools and accessories that are frequently required for CLT construction, as well as good building practices to help contractors build safe and efficient CLT panel structures. Finally, we discuss issues related to the transportation of CLT assemblies from factory to building site. Regulatory aspects of transportation are also discussed. It is importat to note that the lifting, handling, and installation of CLT panels involve multiple interest groups including design professionals, contractors/erectors and CLT manufacturers, each with different areas of interest and expertise. Therefore, the information presented in this Chapter is broad in scope and may or may not be relevant to each interest group.
Cross-laminated timber (CLT) was developed in Europe for the prefabricated construction of wall, roof, and flooring elements. Adaption of CLT for use in the United States requires consideration of the different climates, building codes, and construction methods in this country. ... This Chapter provides guidance on hear, air, and moisture control in wall and roof assemblies that utilize CLT panels in U.S. climate zones. The overarching strategies are to prevent wetting of CLT panels by using drained wall systems, to control airflow using an air barrier on the exterior of the CLT panels, to place rigid insulation to the exterior of the panels, to prevent moisture from accumulating within the panels, and to allow the panels to dry should they get wet. In certain climates, preservative treatment of CLT is recommended to provide additional protection against potential hazards such as decay and termites. ...